Magnetostrictive transducer elements



Aug. 12, 1958 J. M. HERBERT MAGNETOSTRICTIVE TRANSDUCER ELEMENTS Filed April 29, 1957 FIG.

FIG. 2.

United States Patent MAGNETOSTRICTIVE TRANSDUCER ELEMENTS John M. Herbert, Horton, England, assignor to T i1e Plessey Company Limited, Ilford, England, a British company Application April 29, 1957, Serial No. 655,917

2 Claims. (Cl. 310-26) This invention relates to magnetostrictive transducer elements of the type hereinafter called window-frame elements, which consist of four plates two of which extend with their edges between the opposed surfaces of the other two so that an elevation of the element has a shape resembling the Roman figure II.

These elements are used in conjunction with coils wound on the two first-mentioned plates, which may be referred to as legs, and the device is intended to operate by virtue of the vibration of these plates in their longitudinal mode. In order to counteract a tendency of these plates to vibrate in a flexural mode, it has been usual to increase the thickness of these plates adjacent their junction to the transverse plates, and it is an object of the present invention to provide improved window-frame elements, in which flexural-mode vibration of the legs is counteracted by means other than increase of their thickness.

According to the invention the plane of one of the legforming plates is displaced relative to that of the other so that the surfaces of thesetwo plates, while still being both perpendicular to the other two plates, are disposed at an angle to each other. Elements according to the invention may be made by cementing or otherwise joining together fiat slabs of suitable dimensions.

In the drawing accompanying the provisional specification, Figures 1 and 2 are cross-sections showing respectively two forms of a window-frame element incorporating the invention,

Figure 3 of the accompanying drawing is a perspective view of the arrangement of Figure 1, complete with coils.

Referring now first to Figures 1 and 3, the transducer element comprises four flat plates of suitable magnetostrictive material, for example of barium titanate, arranged in two pairs, respectively indicated at 1, 2 and 3, 4, of which the elements 3, 4, are arranged parallel to each other while the other two elements 1, 2, extend at fight angles to the plates 3, 4, opposite edges of each of 2,847,588 Patented Aug. 12, 1958 "ice plates 1 and 2 being secured, for example by cementing, to the opposed surfaces of the plates 3 and 4. A straintransmitting element, for example a gramophone needle 5 clamped by a screw 6 in a bush 7 secured to the outer surface of the plate 3, serves to apply alternating mechanical moments to the plate 3 in such manner as to set up a compression stress in plate 1 and a tension stress in plate 2 and vice versa, while coils 8 and 9 wound on the plates 1 and 2 serve to produce electric voltages or currents corresponding to the variations of the moments applied by means of the needle or the like 5. The arrangement as described up to this point is conventional, but it will be observed in Figure 3 that, contrary to the conventional arrangement, the plates 1 and 2 are not arranged parallel to each other, although each of them is perpendicular to both the plates 3 and 4. In the arrangement illustrated in Figure 3, which corresponds to the sectional plan view of Figure 1, the plates 1 and 2 are inclined by equal but opposite angles to a plane of symmetry indicated by chain-dotted line X. This arrangement greatly counteracts vibrations of the plates 1 and 2 in a flexural mode, which are undesirable for the purposes of the transducer.

In the modified arrangement illustrated in Figure 2 the two coil-bearing plates 11 and 12, which extend between the plates 3 and 4, are arranged at right angles to each other, respectively parallel to two adjacent edges of the rectangular plate 4. It will be observed that this arrange ment is less symmetrical as regards the stresses set up in the two plates 11 and 12 than the arrangement of Figures 1 and 3 is as regards the stresses set up in plates 1 and 2.

What I claim is:

1. A magnetostrictive transducer element of the window-frame type having two leg-forming plates extending with their edges between the opposed surfaces of two end plates spaced in substantially parallel relation, wherein the plane of one of the leg-forming plates is displaced relative to that of the other leg-forming plate, so that the surfaces of these two plates, while being both perpendicular to the two end plates, are disposed at an angle to each other.

2. A window-frame type magnetostrictive transducer element as claimed in claim 1, wherein the two leg plates are arranged symmetrically to a plane arranged perpendicularly to one of the edges of at least one end plate.

References Cited in the file of this patent UNITED STATES PATENTS 2,439,499 Williams a a1. Apr. 13, 1948 

